Covariant quark model for the electromagnetic structure of light nucleon resonances

TL;DR

This paper uses a covariant spectator quark model to estimate electromagnetic transition form factors of light nucleon resonances at high momentum transfer, incorporating lattice QCD data and pion cloud effects, with predictions testable at Jefferson Lab.

Contribution

It introduces a covariant quark model approach to calculate nucleon resonance form factors, combining nucleon parametrizations, lattice QCD data, and pion cloud effects for improved accuracy.

Findings

Good agreement with experimental data for Q^2 > 2 GeV^2.

Uses lattice QCD data for the Δ(1232) resonance structure.

Predictions are relevant for upcoming Jefferson Lab experiments.

Abstract

We present estimates from the covariant spectator quark model for the electromagnetic transition form factors for the resonances $N(1440)\frac{1}{2}^+$, $N(1535)\frac{1}{2}^-$, $N(1520)\frac{3}{2}^-$ and $\Delta(1232)\frac{3}{2}^+$, at intermediate and large square momentum transfer ($Q^2$). The calculations associated to the $N(1440)\frac{1}{2}^+$, $N(1535)\frac{1}{2}^-$ and $N(1520)\frac{3}{2}^-$ states are based exclusively on the parametrizations derived for the nucleon. In the case of the $\Delta(1232)\frac{3}{2}^+$ (isospin 3/2), we use lattice QCD data to estimate the radial structure, and take into account the well known effects associated with the pion cloud dressing of the baryons. Our estimates are based mainly on the valence quark degrees of freedom and are in good agreement with the data for $Q^2 > 2$ GeV$^2$, with a few exceptions. The present predictions can be tested in a near future for large $Q^2$ at the Jefferson Lab -- 12 GeV upgrade.